Hardrock Mining

Early hardrock miners in Nevada used a traditional technology derived from medieval Europe, Spanish Colonial America, and China. They dug open "glory holes" or shallow shafts down to a depth of 100-200 feet to reach the ore body. Once underground, the miners dug "ratholes" to follow the ore body. Miners used gear trains, cams, pistons, and cylinders to construct simple pumping, hoisting, transporting, and grinding machines.

Comstock hardrock miners in the early 1860s introduced industrial technologies, which they exported worldwide during the following decades. Underground mining exploited both hardrock and placer deposits with excavation, support, hoisting, ventilation, and drainage technologies. Before the 1870s, mining ore underground involved driving hand drills into rock and then inserting and firing a charge of black powder. After the explosion, miners mucked out the loosened ore and country rock with picks and shovels. The invention of dynamite in 1867 and the mechanical compressed air rock drill in 1869 revolutionized the excavation process.

Mining underground often created large caverns or "stopes" that tended to collapse. Miners supported stoped-out areas with lumber and unexcavated rock pillars. Philipp Deidesheimer's invention of "square-set timbering" in 1860 is perhaps the best known innovation in mine support technology.

Underground mining demanded a way of hoisting miners and materials up and down the shafts. Early methods ranged from hand carrying sacks of ore up ladders or inclined walkways to simple hoisting machines such as hand cranked windlasses and animal powered whims. Some early mines used small steam engines to pull ore cars up a ramp. Many mines used headframe or gallows-like structures for this purpose. Deep mining on the Comstock in the 1860s and 1870s demanded the use of powerful hoisting engines. Some mines reached depths of more than three thousand feet. Deep mines also used high speed iron "cages" hoisted with flat braided cables to transport miners, ore, and equipment up and down the mine shafts.

Underground mining requires technologies to manage air and water. Mine ventilation technologies included both draft and forced air ventilation systems. Draft ventilation worked somewhat like a siphon with outside openings funneling air into and out of the mine. Early mines used hand bellows and wind sails but after the 1860s, engine-powered fans and blowers ventilated mines.

Many underground mines flooded. The earliest drainage techniques involved "bailing" systems using buckets raised with hoisting machines, "water skips" pulled up inclined ramps, and digging tunnels that channeled water to the outside. Other mines used engine-powered pumps. Deep industrial mines employed large Cornish pumps (single action vacuum piston "force-action" pumps). Double action pumps replaced Cornish pumps by the end of the nineteenth century.

The introduction of open pit mining with power shovels, first developed in the Mesabi Iron Range in Minnesota and later at the Bingham pit in Utah, greatly changed hardrock mining in some places by the early twentieth century. Open pit operations dominated hardrock mining in Nevada by the end of the twentieth century.

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